Sol–gel synthesis of lithium aluminum silicate powders: The effect of silica source

Lithium aluminum silicate (LAS) powders were synthesized through sol-gel technique by using three different sources of silica, i.e., TEOS, fumed silica and rice husk ash and their effects on the characteristics of the powders were studied. The gel and oxide powders were characterized by thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). DTA and XRD results showed that the crystallization of beta-eucryptite and beta-spodumene started at about 700 degrees C for TEOS and fumed silica sources while the same crystallized at about 785 degrees C for rice husk ash source. FTIR study confirmed the presence of nonbridging oxygen in AlO6 octahedra for beta-eucryptite prepared from TEOS source calcined at 400-600 degrees C and the same was found for fumed silica and rice husk ash sources calcined at 400-1000 degrees C. SEM showed the formation of cobblestone-like morphology of beta-spodumene obtained from three different sources of silica.